In a fingerprint input transducer or sensor, the finger under investigation is usually pressed against a flat surface, such as one side of a glass plate, and the ridge-valley pattern of the finger tip is sensed by some sensing means such as an interrogating light beam. The processing of the fingerprint information thus obtained may comprise laser techniques.
Fingerprint identification devices of this nature are generally used to control the access of individuals to information (information access control), for instance, computer terminals, or to buildings (physical access control).
One of the problems associated with fingerprint sensors concerns the reliable and accurate transformation of the ridge-valley pattern of the finger tip into electrical signals. Optical techniques which are widely used require a high amount of sophisticated equipment. Simple electromechanical sensors are sometimes not sensitive enough.
Therefore, there is a need for a fingerprint input sensor or transducer which is adapted to reliably sense the fingerprint relief and transform the sensed information into electrical signals. The fingerprint sensor should be of simple structure.